Self-developing pocket radiation dosimeter



Dec. 30, 1952 K. G. STERN 2,624,011

SELF-DEVELOPING POCKET RADIATION DOSIMETER Filed March 27, 1951 WM A Patented Dec. 30, 1952 SELF-DEVELOPING POCKET RADIATION DosIMErEn Kurt G. Stern, New York, N. Y.

Application March 27, 1951, Serial No. 217,710

(Cl. E50-65) 16 Claims.

This invention relates to radiation detecting devices, and more particularly to a radiation detector of the photographic type.

A `main object of the invention is to provide a novel and improved radiation detector of the photographic type having self-contained means for developing the photographic element thereof.

A further object of the invention is to provide an improved radiation detector of the photographic type having self-contained means for developing the radiation-sensitive element thereof, said detector being simple in construction, compact in size, and easy to manipulate.

A still further object of the invention is to provide an improved radiation detecting unit of the self-developing type, wherein no darkroom facilities are required to develop the radiation-sensitive element thereof and wherein said element is eiectively shielded from visible radiation at all times prior to development thereof, whereby false and Vmisleading indications are avoided.

A still further object of the invention is to provide an improved radiation detector of the photographic type which may be conveniently worn or carried byl an individual in order to detect or gauge exposure of the individual to ionizing radiation, such as gamma radiation, said detector having self-contained means for developing the radiation-sensitive element thereof, and having means for shielding said element against light during the process of development thereof as well as during the period of normal wearing thereof by the individual', whereby no darkroom facilitiesr are required for developing the element to determine the degree of exposure thereof to ionizing radiation, the device incorporating its own developing chemicals and being arrange-d so that said chemicals may be readily and conveniently utilized in the unit when it is desired to develop said radiation-sensitive element.

A still further object of the invention is to provide. an improved radiation detector of the photographic type having self-contained means for developing the radiation-sensitive element thereof', Vsaid detector comprising inexpensive parts, being' reliable in operation, and being usable over and over again by the renewal ofthe disposable elements thereof.

Further objects and advantages of the invention will become apparent from the following description and claims, and from the acompanying drawings, wherein:

Figure 1 is a front elevational View of an improved' self-developing pocket radiation dosimeter constructed in accordance with the present invention.

Figure 2 is a cross-sectional view taken on line 2 2 of Figure l.

Figure 3 is a perspective View, partly broken away, of one form of cartridge for developing materials which may be employed in the dosimeter of Figures l and 2.

Figure 4 is a perspective view of the dosimeter of Figures l and 2 with the developer end cap and developer cartridge removed,

Figure 5 is an enlarged cross-sectional View taken on line 5 5 of Figure 2.

Figure 6 is a perspective view of the dosimeter of Figures l and 2, partly broken away, and showing the indicator end plug and the photographic element partly withdrawn from the casing of the dosimeter subsequent to development of the photographic element.

Figure 7 is a front elevational view of a photographic element employed in the dosimeter, said element being shown in its unrolled position.

Figure 8 is a longitudinal cross-sectional view takenv through an alternative form of developer cartridge which may be employed in the pocket dosimeter of the present invention.

Figure 9 is an enlarged longitudinal cross-sec- `tional view taken through the lower portion of a modified formv of radiation dosimeter unit constructed in accordance with the present invention.

Reference is made to applicants copending applications, Serial No. 182,830, led September l, 1950, for Radiation Detector, and Serial No. 215,053, filed March 12, 1951, for Film Badge Radiation Detector, containing related subject matter, and containing descriptions of associated types of radiation detectors employed for purposes similar to that for which the radiation dosimeter of the present invention is employed.

Referring to the drawings, the improved radiation detecting unit is designated generally at H. The unit H comprises a cylindrical housing l2, in one end of which is removably secured the plug member i3. Said plug member has a reduced inner portion lf3 and is secured in the end of housing l2 in any suitable manner, Ias for example, by a tight friction t. Secured to the reduced inner portion of plug member I3, as by a plurality of strips of adhesive tape I5 is the cylindrically-rolled radiation indicator tab It. Tab I6 comprises a rectangular flexible cardboard body Il on which is longitudinally `and centrally secured a strip IS of photographic paper, such as Kodabromide No. 4 paper, as manufactured by the Eastman Kodak Company, Rochester, New York. As shown in Figure 7, the test strip I8 is flanked on both sides by a Exposure Range in Roentgens Scale Step Designation The gamma, exposure ranges marked on the comparison scale shown in the above table may obviously be modified to fulfill specific requirements of the medical authorities, or to correspond more closely to the radiation response characteristics of the photographic material employed.

For further details concerning the construction and use of the radiation detector tab I6, reference is made to applicants copending application, Serial No. 215,053, filed March l2, 1951, as mentioned above.

As shown in Figures 5 and 6, the indicator tab I6 may be curled into -a generally cylindrical shape with the radiation sensitive element I8 facing inwardly.

Designated at 20 is an axially extending sleeve member which is rigidly carried by a bushing 2| threadedly secured in the end of housing I2 at the end thereof opposite plug member I3. An annular sealing gasket 22 may be employed between the head of bushing 2| and the rim of housing I2, as shown in Figure 2. The sleeve member 20 extends substantially the entire internal length of housing I2 between plug niember I3 and bushing 2 I, .and is formed with a 1ongitudinal slot 23 located adjacent to and substantially midway between the side edges I9, I9 `of the indicator tab IIE when the parts are assembled in the manner shown in Figure 5. The plug member I3 and housing I2 may be provided with registrable index marks 24 and 25 to insure the proper registration of the slot 23 with the space between the tab edges I9, I9 when the unit is thus assembled. With the slot 23 in this position, the cylinder 20 acts as a light trap, making it possible to open the dosimeter in bright daylight or artificial light Without exposing the photographic strip I8 to actinic light.

Designated at 26 in an inner hollow cylinder or cartridge, containing developing' materials, which is contained in the sleeve 2|). A closure plug 21 is axially threaded into the bushing 2|. The bushing 2| is formed with a conical, funnellike surface 28 and the plug 2l is provided with a mating conical surface 29 which is sealingly engageable with funnel surface 28.

The cartridge 26 may comprise a deformable plastic shell having frangible ends, said shell containing xing solution and an inner capsule 3B of frangible, deformable plastic material containing developing powder. The housing I2 and the inner cylinder 20 may be of any suitable light-opaque, rigid material, such as thin metal or plastic. The housing I2 is of a material which is opaque to visible light but penetrable to gamma radiation, such as thin aluminum or plastic tubing. The housing I2 may be provided with a con` l4 ventional pocket clip 3|, whereby the unit may be carried in the users pocket in the manner of a fountain pen.

Whene it is desired to process the radiationindicator tab I'S, the closure plug 2l is unscrewed and the cartridge 26 is removed. Said cartridge is squeezed or otherwise manipulated to break the inner capsule 30, and one end of the cartridge is broken. The contents of the cartridge are emptied into the housing I2 through the funnel like opening of bushing 2|. The closure cap 2'I is then screwed into the bushing 2| into sealing position thereon and the unit is thoroughly shaken to bring the developing materials into contact with the photographic strip I3 for Ia suiiicient length of time to completely develop strip I8. The plub member I3 is then withdrawn from the end of housing I2, whereby the indicator tab I6 is removed from said housing, as shown in Figure 6. The tab I6 is then detached from the plug I'S and may be then examined to determine the degree of exposure of the unit to ionizing radiation.

As an alternative, the inner cartridge may comprise a deformable, frangible plastic shell 26 provided With a transverse inner partition Wall 2l', as shown in Figure 8, dividing the cartridge into two compartments. One compartment may contain developing solution 23 and the other compartment may contain fixing solution 29. In processing the indicator strip, the cartridge is removed and the left end of the cartridge is rst broken. The developer solution is poured into the housing through bushing 2| and plug 2'I is secured thereon. The unit is shaken thoroughly for a sufficient period to develop the photographic strip I8. The plug 27 is then removed, the other end of cartridge shell 26 is broken, and the fixing solution 29 is introduced into the housing I2 through bushing 2| The plug 21 is replaced and the unit is shaken thoroughly to fix the developed strip I8. Plug I3 may then be removed to withdraw the indicator tab I6 for examination, as above described.

As a further alternative, the partition wall 21' may be relatively thin and frangible. When the developing materials are to be introduced into the housing, the cartridge 26 may be squeezed so as to break said partition wall, and the contents of the cartridge may then be squeezed out of one end thereof into the housing through bushing 2 I,

After use of the unit, the internal parts thereof may be cleaned and the unit may be retted in a suitable darkroom with a new indicator tab I6. A new cartridge of developing and fixing materials is then provided in the sleeve 20, whereby the unit is ready for further use.

In the modified form of the pocket dosimeter illustrated in Figure 9, an equalizing lter 32, made of suitable metal, such as sheet cadmium, lead or silver, in the form of a band, may be provided between the outer housing shell, shown at I2', and the strip of photographic material I8. Where cadmium is employed, the preferred thickness of the band 32 is 1 mm. The filter 32 protects the photographic emulsion of strip I8 against hard beta and soft gammal rays and also acts to insure that the photographic emulsion will register equal amounts of gamma radiation with the same density independently of the Wave length over a Wide range of the gamma energy spectrum (from approximately 0.1 to 10 m. e. v.). As shown in Figure 9, the bottom of the housing of the unit may comprise a disc 33, secured to the housingbody by alayer 3 4 ofgsuitable sealing composition, such as isiconveniently employed in sealing corkson bottles. Thiscomposition may bev appliedin a liquid state by-dipping the shell, With the ydisc 33 in place thereon, into the molten sealing mixture. Shellac, sealing wax, and cellulose plastics are suitable materials for seals of this type. Thesnished seal may be marked by impressing. a. date or other information onto its periphery. When the dosimeter is opened to remove the` indicator tab for examination after processing, the seal would be fractured, thus indicating thatthe device had been opened.

Theinner chemical` cartridge` may take many dilierentformadepending onthe contents and lvvithasingle.develcperfixer (or stabilizer)v cornposition, employing a single compartment inthe cartridge, or the components may beseparated by, employinganinner capsule or a partition wall suche-5,27' in Figure 8.

As above explained, the, slotted inner cylinder 2l) functions as a light trap, making it possible to open the'dosirneter at the top (by removing plugA 2l) in bright daylight or artificial light for the purpose of removing the cartridge of developingmaterials and emptying its contents into the inner cylinder El) without exposing, the photographic strip i8' to actinic light.

It will be further noted that the 'photographic strip I8 is preferably arranged parallel to the axis of the dosimeter shell and is located opposite the slot 23 of the inner cylinder 2li. In this manner, any actinic radiation which may enter the dosimeter upon removal of plug 2f! is prevented from reaching. the strip I8 through the slot 23. Theprimary function of said Slot is to admit the processing chemicals from the cartridge 25 or 2S intothe annular space betweenthe inner and outer cylinders, and at the same time to allow air to escape from the annular space intov the upper portion oi inner cylinder 2F). Theabove arrangement prevents air from being trapped inthe annularspaceand interfering with the developing process.

In the arrangement of Figures 2 and 6, the indicator taby l is shown attached to the reduced portion ld of plug i3 with the photographic strip I8 facing inward. Alternatively, the tab l5 may besecured to the inner wall surface of outer cylinder l2 with strip IS. facing inwardly or to the outer. surface of. inner cylinder 2@- with strip lil facing'` outwardly, whereby sunicient clearance will be provided. adjacent the surface of strip IS to allow proper-access of the developing chemicals to the photographic strip during the processing of the indicator tab. Experiments have indicated that at least two millimetres clearance is required in order to insure free access of the chemical solutions to the photographic strip and to avoid the trapping of air bubbles on the surface thereof.

While certain speciiic embodiments of an irnproved poclfret radiation dosiineter have been disclosed in the foregoing description, it will be understood that various modifications within the spirit oi the invention may occur to those skilled in the art. Therefore it is intended that no limitations be placed on the invention except as defined by the scope of the appended claims.

What is claimed is:

l. In a radiation detector, an elongated houslng of material opaque to light and penetrable to ionizing radiation, an elongated light-opaque sleeve secured longitudinally in said housing and 6 defining a space between the,v sleeveandv theinftermal surface of the housing, said sleeve opening at one end'of the housing, aradiationesensitive. tab elementin said space arranged around said sleeve, and means covering the other end o f the housing.

2, In a radiation detector, an elongatedhousing of material opaque to visi-ble light and penetrable to ionizing radiation, an elongated core-member secured. longitudinally in said'housing and deiining a spacebetween the core member and the internal surface of the housing, and a radiation-sensitivev tab element in said space arranged around said core member.

3. In. a` radiation detector, an elongatedhousf ing of material opaque to Visible lightv and penetrable toionizing radiation, anA elongatedv sleeve member secured longitudinally in saidV housing defining a space between the sleeve member and thev internal surface of the housing,y and a radiation-sensitive tab elementin said space arranged around said sleeve member.

4. In a radiation detector, an elongated housing of material opaque to visible light and penetrable to ionizing radiation, an elongated sleeve member secured longitudinally in said housing and dening a space between the'sleeve member and the internal surface of the housing, and a radiation-sensitive ta'b element in said space arranged around said sleeve member, said sleeve member opening at one end of said housing.

5. In a radiation detector, an elongated housingl yof material opaque to visible light and penetrable to ionizing radiation, an elongated sleeve member secured longitudinally in said housing and defining a space between the sleeve member and the internal surface of the housing, radiation-sensitive tab element in said space arrangedaround said sleeve member, said sleeve member opening at one end of the housing and being formed in its wall with an aperture located opposite said tab element,

6. In a radiation detector, an elongated housing of material opaque to visible light and penetrable to ionizing radiation, an elongated sleeve member secured longitudinally in said housing and defining a space between the` sleeve member and the internal surface of the housing, a radiation-sensitive tab element in said space arranged around the sleeve member, said sleeve member opening at one end of the housing and being formed in its wall with an aperture located opposite said tab element, and an elongated, frangible container disposed inside said sleeve member, said container being adapted to carry developing materials.

7. In a radiation detector, a tubular housing of material opaque to light andY penetrable to ioniz ing radiation, an annular bushing secured to one end of said housing, a sleeve member secured to said bushing and extending longitudinally in said housing, lsaid sleeve member deiining an annular space between 'the sleeve member and the internal surface of the housing, a photographic tab element in said space arranged around said sleeve member,l and means covering the other end of said housing, said sleeve member being formed with a longitudinal slot located opposite said tab element.

S, In a radiation detector, a tubular housing of material opaque to light and penetrable to ionizing radiation, an annular bushing secured to one end of said housing, a sleeve member secured to said bushing and extending longitudinally in said housing, said sleeve member defining an annular space between the sleeve member and the internal surface of the housing, a photographic tab element in said space arranged around said sleeve member, means covering the other end of said. housing, said sleeve member being formed with a longitudinal slot located opposite said tab element, whereby the sleeve member denes a light trap, an elongated, frangible container disposed in said sleeve member, said container being adapted to carry developing materials, and a plug member detachably secured in said bushing.

9. In a radiation detector, a tubular housing of material opaque to light and penetrable to ionizing radiation, an annular bushing secured to one end of said housing, a sleeve member secured to said bushing and extending longitudinally in said housing, said sleeve member denning an annular space between the sleeve member and the internal surface of the housing, a closure plug removably secured in the other end of said housing, and a photographic tab element secured to said plug and arranged around said sleeve member in said space.

10. In a radiation detector, a tubular housing of material opaque to light and penetrable to ionizing radiation, an annular bushing secured to oneend of said housing, a sleeve member secured to said bushing and extending longitudinally in said housing, said sleeve member delining an annular space between the sleeve inember and the internal surface of the housing, a closure plug removably secured in the other end of said housing, and a photographic tab element secured to said plug and arranged around said sleeve member in said space, said sleeve member being formed with a longitudinal slot located opposite said tab element, providing a passage for the ow of developing liquid into said annular space while preventing light from reaching the tab element.

1l. In a radiation detector, a tubular housing of material opaque to light and penetrable to ionizing radiation, an annular bushing secured to one end of said housing, a sleeve member secured to said bushing and extending longitudinally in said housing, said sleeve member denning an annular space between the sleeve member and the internal surface of the housing, a closure plug removably secured in the other end of said housing, a photographic tab element secured to said plug and arranged around said sleeve member in said space, said sleeve member being formed with a longitudinal slot located opposite said tab clement, providing a passage for the flow of developing liquid into said annular space while preventing light from reaching the tab element, an elongated, frangible container disposed in said sleeve member, said container being adapted to carry developing materials, and a plug member detachably secured in said bushing.

12. In a radiation detector, a tubular housing of material vopaque to light but substantially transparent to ionizing radiation, a core member longitudinally secured in said housing and dening a space between the core member and the internal surface of the housing, a photographic tab element in said space arranged around said core member, an equalizing lter of sheet material partially opaque to ionizing radiation arranged between said tab element and the internal surface of said tubular housing.

13. In a radiation detector, a tubular housing of material opaque to light but substantially transparent to ionizing radiation, a tubular core member longitudinally secured in said housing, and deiining a space between the core member and the internal surface yof the housing, a photographic tab element in said space arranged around said core member, an equalizing filter of sheet material partially opaque to ionizing radiation arranged between said tab element and the internal surface yof said tubular housing, said core member being formed with an aperture located opposite the tab element, providing a passage for the flow of developing liquid into said space while preventing light from reaching the tab element, and a removable plug element secured in one end of said core member.

14. In a radiation detector, a tubular housing of material opaque to light but substantially transparent to ionizing radiation, and a hollow core member longitudinally secured in said housing and dening a space between the core member and the internal surface of the housing, said core member being formed with a longitudinal slot, said core member being adapted to receive developing liquid and said slot defining a passage for the ilow of developing liquid from said core member into said space.

l5. In a radiation detector, a tubular housing of material opaque to actinic light but substantially transparent to ionizing radiation, and a hollow sleeve member longitudinally secured in said housing and dening a space between the sleeve member and the internal surface cf the housing, said sleeve member extending `for the major portion of the internal length of said housing and being formed with a longitudinal slot, said sleeve member being adapted to receive developing liquid and said slot dening a passage for the now of developing liquid from the sleeve member into said space.

16. In a radiation detector, a tubular housing of material opaque to actinic light but substantially transparent to ionizing radiation, a hollow core member longitudinally secured in said housing and dening a space between the core member and the internal surface of the housing, said core member being formed with a longitudinal slot, said core member being adapted to receive developing liquid and said slot dening a passage for the now of developing liquid from said core member into said space, and a removable plug element secured in the end of said core member.

KURT G. STERN.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,483,991 Wollan et al Oct. 4, 1949 2,496,218 Kieffer Jan. 31, 1950 2,500,422 Land Mar. 14, 1950 2,565,378 Land Aug. 21, 1951 

